Problem: Constraints

* H is an integer between 2 and 50 (inclusive).
* W is an integer between 2 and 50 (inclusive).
* s_{i, j} is `.` or `#` (1 \leq i \leq H, 1 \leq j \leq W).
* s_{1, 1} and s_{H, W} are `.`.

Input

Input is given from Standard Input in the following format:


H W
s_{1, 1}s_{1, 2}s_{1, 3} ... s_{1, W}
s_{2, 1}s_{2, 2}s_{2, 3} ... s_{2, W}
:   :
s_{H, 1}s_{H, 2}s_{H, 3} ... s_{H, W}


Output

Print the maximum possible score that Snuke can achieve, or print -1 if the game cannot be completed.

Examples

Input

3 3
..#
#..
...


Output

2


Input

3 3
..#
..
...


Output

2


Input

10 37
.....................................
...#...####...####..###...###...###..
..#.#..#...#.##....#...#.#...#.#...#.
..#.#..#...#.#.....#...#.#...#.#...#.
.#...#.#..##.#.....#...#.#.###.#.###.
.#####.####..#.....#...#..##....##...
.#...#.#...#.#.....#...#.#...#.#...#.
.#...#.#...#.##....#...#.#...#.#...#.
.#...#.####...####..###...###...###..
.....................................


Output

209

Solution (in PYTHON3):

Solution:
from collections import deque
H,W=map(int,input().split())
Map=[list(input()) for i in range(H)]
for h in range(H):
  Map[h].insert(0,"#")
  Map[h].append("#")
Map.insert(0,["#"]*(W+2))
Map.append(["#"]*(W+2))
white=sum(Map[i].count(".") for i in range(H+2))

Que=deque([(1,1,1)])
visited=[[10**10]*(W+2) for i in range(H+2)]
while Que:
  x,y,stage=Que.popleft()
  if x==W and y==H:
    print(white-stage)
    exit()
  stage+=1
  for i,j in ((x+1,y),(x-1,y),(x,y+1),(x,y-1)):
    if Map[j][i]=="." and stage<visited[j][i]:
      visited[j][i]=stage
      Que.append((i,j,stage))
print(-1)